Direct-action fuse for a projectile



March 13 1956 E. T. GRABERG DIRECT-MOTION FUSE FOR A PROJECTILE Filed Jan. 21, 1953 lll/117 {Illillllllllla IN VEN TOR.

glllflllflllf ERIC TORGNY GRBERG BY Z ATTORNEY DIRECT-ACTIQN FUSE FR A PROJECTHLE EricTol-gny Graherg, Karlskoga, Sweden, assigner to Aktiebolaget Bofors, Bofors, Sweden, a Swedish corporation Application .lanuary 21, 1953, Serial No. 332,311

Claims priority, application Sweden March 14,1952

Claims. (Cl. IGZ- 78) The present invention relates to direct-action fuses for projectiles, more particularly to safety devices associated with or included in such fuses.

With direct-action fuses as hitherto known, it is standard practice to place the fuse charge which is to be detonated by the striking pin as far back in the fuse as possible as otherwise the charge may be detonated by an accidental impact even though it is secured against detonation by the striking pin. Placement of the charge in the rear part of the fuse has the disadvantage that it entails the use of a long striking pin which in turn delays the setting of the fuse charge. This delay is primarily due to shock or pressure wave formed by the impact experienced by the projectile and acting upon the striking pin thereof so that a certain period of time must elapse before the pin can ignite the fuse charge. It has also been found that this shock wave may be transmitted to the wall of the projectile proper and may travel along this wall for a considerable distance before the fuse charge is ignited. Such shock wave progressing along the wall of the projectile may result in serious damage to the projectile, in particular it may destroy the cone of the projectile, especially of a projectile of the hollow charge type.

It will now be apparent that it would be highly desirable to place the fuse charge as closely as possible to the apex or tip of the fuse as such position of the charge would result in a more rapid ignition of the fuse and at the same time reduce the danger of a destruction of or damage to the cone of the projectile by a shock wave. However, prior to the present invention it was not possible to place the fuse charge in its most desirable position as there were not available safety means adequately protecting the fuse charge against a detonation by an accidental impact.

The principal object of the present invention is to provide novel and improved safety means for a direct action fuse of the general type above referred to which permit positioning of the fuse charge close to the tip of the fuse without unduly increasing the danger of a premature detonation by an accidental impact.

Another object of the invention, allied with the preceding one, is to provide a fuse design Which permits the use of an extremely short striking pin thereby assuring a rapid ignition of the fuse charge.

Still another object of the invention is to provide novel and improved safety means which protect the fuse of the projectile against accidental detonation until the projectile is tired and which is automatically released when the projectile is fired thereby arming the same.

Another more specic object of the invention is to provide a safety means which after its automatic release is ejected from the projectile.

"um Other and further objects, features and advantages of the invention will be pointed out hereinafter and set forth in the appended claims forming part of the application.

In the accompanying drawing a now preferred embodiment of the invention is shown by way of illustration and not by way of limitation.

In the drawing:

Fig. 1 is a perspective sectional view of a direct-action fuse equipped with a safety means according to the invention showing the safety means in its position protecting the fuse charge against accidental detonation.

Fig. 2 is a section taken on line 2-2 of Fig. l.

Fig. 3 is a perspective sectional view similar to Fig. l showing the safety means partly released after thev firing of the projectile.

Fig. 4 is a perspective sectional view showing the fuse after the completion of the release of the safety means andI the ejection thereof, and

Fig. 5 is a sectional view of the ejected components of lthe safety means.

Referring now to the figures in detail, the exemplified direct-action fuse comprises a hollow outer fuse casing 1 in which is centrically tted a hollow cylindrical body 2 either' integral withA casing 1 or secured thereto, as shown, by a screw connection. Cylinder 2 is lled with a blasting charge 3. The solid forward end of cylinder 2 is formed with a bore transverse to the longitudinal axis l of the fuse. A. cylindrical. body 4 is rotatably inserted in thisV bore. Cylinder 4 is provided at each end with a segment 5 and 6 respectively forming pivots for the cylinderl and` having a cross-sectiony less than half of a semi-circle.

therethrough in which is inserted a fuse charge 7. An axial hole 8 in the foremost end of cylinder 2 extends into the bore for fuse charge 7. As is shown on Fig. 4, hole 8 is in connection with the blasting charge 3 when the fuse charge 7 and the hole therefor are in axial position while the material of cylinder 4 separates hole 8 from theblasting charge when the fuse charge 7 and its hole are intransverse position as is shown on Fig. l'. Axial hole 8- serves to receive a striking pin 9 which is shownl as being tapered at both ends. As will be observed, the fuse charge is positioned near the tip of the directvaction fuse and the striking pin is extremely short in The fuse casing 1 should be visualized as being secured upon the casing of the projectile proper which is not shown.

The safety means proper comprise a protective hollow hood or nose 15 which fits over the pin 9 and the portion of cylinder 2 protruding from the forward end of casing 1. Nose 1S complements the truncated casing to form the cone of the projectile and is provided with a cylindrical extension sleeve 15' extending into casing 1 and litted upon cylinder 2 when the nose is in the position of Fig. 1. The extension sleeve 15 has one or more transverse holes 16 and two axial slots 22. These slots serve to receive segments 5 and 6 when the same are in the position of Fig. l thereby securely retaining fuse charge 7 in its transverse position which may be referred to as the safety position of the fuse charge. The lower edge of the sleeve 15 is formed with one or more spherically curved inden- 'tations 19 or a continuous spherically curved groove.

A second sleeve 12 which serves with a tight iit in casing 1 and has at its upper end an inwardly extending ange 11 which is in engagement with the lower edge of sleeve 13. A loaded coil spring abutting with one end against the bottom of casing 1 and with its other end against flange 11 serves to bias sleeve 12 against sleeve 13 or in other words in the direction for moving sleeve 13 out of casing 1. The safety means finally comprise locking elements shown as balls 17 and 20. Balls 17 are inserted in transverse holes 16 of sleeve 15' which holes in effect form a cage for balls 17. Balls 17 also engage recesses or indentations l in cylinder 2 when the components of the safety means are in the positions of Fig. l. Similarly, balls 20 engage indentations or recesses 21 in cylinder 2 and are held between the lower edge of sleeve 15 and flange 11 in the position of Fig. l. This figure also shows that sleeve 13 retains balls 17 and 20 in their respective indentations 18 and 21 in cylinder 2 thereby locking all the components of the direct-action fuse in the positions of Fig. 1. It will be evident that as a result the firing pin is protected against impact and the fuse charge is also protected by the heavy wall of nose or hood 15.

The direct-action fuse and the safety means thereof, as hereinbefore descibed, function as follows.

Let it be assumed that a projectile with a direct-action fuse according to Fig. 1 is tired. At the moment of ring and immediately thereafter, the forces of acceleration acting upon the direct-action fuse will be so great that sleeves 13 and 12 will be axially displaced within casing 1 against the action of spring 10 which accordingly is more strongly compressed. Furthermore, the centrifugal forces acting upon balls 17 and 20 due to the rotation which is imparted to the projectile by the riing of the gun barrel from which it is tired will cause the balls to press against sleeve 13 which pressure will be transmitted to the inside wall of casing 1. The centrifugal force acting upon the balls will also cause the same to leave their respective indentations 18 and 21 in cylinder 2, space being made available by the axial displacement of sleeves 13 and 12 toward the bottom of casing 1. As the forces of acceleration gradually diminish, the strongly compressed spring overcomes the forces of acceleration and pushes sleeves 12 and 13 toward the open end of casing 1.

As a result, sleeve 13 is coupled with sleeve 15' of nose 15 by balls 2l) which are now seated in the indentations 14 and 19 in sleeves 13 and 15 respectively. Consequently, nose 15 is being pushed out of casing 1. Fig. 3 shows sleeves 12 and 13 still partly retracted but already having moved forwardly a certain distance so that nose' 15 is partly lifted out of casing 1. As the forward movements of the sleeves 12 and 13 continue by the action of spring 10, nose 15 will be first ejected to be followed by balls 17 and 20 and iinally by sleeve 13. Fig. 5 shows the aforementioned parts after ejection from the casing 1.

It will be apparent that ejection of nose 15 releases segments 5 and 6 which were formerly held by slots 22 of sleeve 15'. As now sleeve 12 moves toward the position of Fig. 4 ange 11 of this sleeve engages segments 5 and 6 thereby turning the same into the position of Fig. 4 in which ange 11 abuts against the flat side of segments 5 and 6 and fuse charge 7 is in axial position which is the action position of the fuse. In other words, the fuse charge is in alignment with the striking pin 9 and the blasting charge 3. The striking pin 9 is now exposed and the fuse is armed so that by an impact upon the striking pin the fuse charge and with it the blasting charge will be detonated in a very short period of time by reason of the short striking pin and the location of the fuse charge near the forward end of the fuse.

While the invention has been described in detail with respect to a certain now preferred example and embodiment of the invention it will be understood by those skilled in the art after understanding the invention, that various changes and modifications may be made without departing from the spirit and scope of the invention, and

it is intended, therefore, to cover all such changes and modifications in the appended claims.

What is 'claimed as new and desired to be secured by Letters Patent, is:

1. A safety device for a direct-action fuse for a projectile including a fuse Vcharge and a striking pin for detonating the fuse charge, the said safety device comprising a protective hood covering the striking pin, and locking means releasably locking said protective hood to the body of the fuse and operable for automatic release of the hood when the projectile is in flight, the said locking means being responsive to and controlled by the axial forces of acceleration acting upon a projectile in ight for releasing the locking means when the initial maximum forces of acceleration have decreased below a predetermined value. Y

2. A safety device for a direct-action fuse for a projectile including a fuse charge and a striking pin for detonating the fuse charge disposed in the body of the fuse, the said safety device comprising a protective hood covering the striking pin, and locking means releasably locking said hood to the body of the fuse, the said locking means including retaining members disposed between said hood and the fuse body in positions locking the protective hood to the fuse body and movable into positions releasing the hood from the fuse body when projectile is in flight, the said retaining members being responsive t'oand controlled by the forces of acceleration acting upon a red projectile in axial direction for releasing the hood when the initial maximum forces of acceleration have decreased below a predetermined value.

3. A safety device according to claim 2, wherein the said protective hood is movably fitted in the fuse body, and wherein spring means within the fuse body biased in axial direction opposite to the direction of the axial forces of acceleration coact with the said hood so as to urge the same out of its position in the fuse body, and wherein the said retaining members when in the said locking positions retain the protective hood within the fuse body against the action of said spring means and when moved into the said release positions by the forces of acceleration release the spring means for ejection of the hood from the fuse body when the forces of acceleration have decreased below said predetermined value at which value the spring bias overcomes the forces of acceleration.

4. A safety device according to claim 3, wherein the said fuse charge is disposed shiftably between an action position and a safety position, and wherein the said protective hood is operatively coupled with said fuse charge for control of the position of the latter, the said protective hood when locked to the fuse body by said locking means retaining the fuse charge in its safety position and when released from the fuse body releases the fuse charge for movement into its actionl position.

5. A direct-action fuse for a projectile comprising in combination a fuse casing attachable to a projectile, a fuse charge disposed within the casing near the -forward end thereof, a striking pin protruding from an opening in the (fuse casing and coacting with the fuse charge for detonating the same by an impact against the striking pin, a protective nose fitted over the striking pin for protecting the latter and the fuse charge against accidental impact, the said nose being movably fitted in the casing, and locking means between said nose and said fuse casing releasably retaining the nose in its protective position and operable for release of the nose when the projectile is in flight, the said locking means being responsive to andV controlled'by the forces of acceleration acting upon a tired projectile in axial direction for releasing the nose when the initial maximum forces of acceleration have end thereof, a striking pin protruding from an opening in the fuse casing and coacting with the fuse charge for detonating the same by an impact against the striking pin, a protective nose tted over the striking pin for protecting the latter and the fuse charge against accidental impact, the said nose being movably iitted in the casing, spring means within the fuse casing coacting with the nose and biasing the same toward an axial position uncovering the striking pin, locking means engaging said nose and releasably retaining the same in its protective position against the action of the spring means, and release means within the casing coacting with the locking means for release of the latter when a projectile bearing the fuse is in flight, the said release means being responsive to and controlled by the forces of acceleration acting upon the fuse in an axial direction opposite to the action of the spring means for releasing the locking means and rendering the spring means operative for the purpose aforesaid when the forces of acceleration have decreased below the force of the spring means.

7. A direct-action fuse according to claim 6, wherein the said locking means comprise locking elements engageable with said protective nose and said casing and a retaining member releasably retaining the locking elements in engagement with the nose and the casing for locking the nose to the casing, and wherein the said release means comprise a release member slidably tted in said casing and biased by said spring means against said retaining member, the said retaining member and the said release member being slidable by the axial action of the forces of acceleration into positions relative to said casing in which said locking elements are released from engagement with said casing thereby causing the spring means to move the nose toward its position uncovering the striking pin.

8. A direct-action fuse according to claim 7, wherein the said nose has a sleeve-shaped portion extending into said casing, and the said casing has a cylindrical center portion encompassed by said sleeve portion, the said sleeve portion having a recess forming a cage for said locking elements and the said cylindrical portion including a recess engageable with locking elements placed in said cage.

9. A direct-action fuse according to claim 8, wherein the said retaining member is in form of a sleeve fitted axially slidable in an annular space between the sleeve portion of the nose and the casing for retaining the locking elements in said recesses when the nose is in its protective position, and wherein the said release member is in form of a sleeve fitted axially slidable in an annular space between said casing and said cylindrical portion thereof and biased by said spring means into an axial position slidably holding said retaining sleeve in the said retaining position, the said two sleeves being retractable by the forces of acceleration into axial positions relative to the casing in which said retaining sleeve releases said locking elements from said recesses.

10. A direct-action fuse according to claim 9, wherein the said locking elements couple the retaining sleeve with said sleeve portion of the nose upon release of the latter for pushing the nose out of the casing by a movement of the retaining sleeve and the release sleeve toward the forward end of said casing opening owing to an expansion of said spring means upon a decrease of said axial forces of acceleration.

ll. A direct-action fuse according to claim 1), where in the said locking elements are ball shaped, andy wherein the facing ends of 4said sleeve portion of the nose and the retaining sleeve are each shaped so as to receive therebetween at least one of said balls for effecting the said coupling between the sleeve portion of the nose and the retaining sleeve.

l2. A directwaction fuse according to claim 6, wherein the said fuse charge is fitted in a cylinder disposed within said cylindrical portion of the casing rotatable between an action position and a safety position of the fuse charge, and wherein the said nose is operatively coupled with said cylinder for retaining the fuse charge in its safety position when the nose is retained in the casing, the said nose when released from the casing releasing said cylinder for rotation of the fuse charge into its action position.

13. A direct-action tuse according to claim u, wherein the said cylindrical portion of the casing is formed with a center portion having a transverse bore, tne said cylinder with the fuse charge being rotatably fitted in said bore, and wherein the said nose has a sleeve-shaped extension slidably fitted between said casing and said center portion thereof, the said sleeve-shaped extension including an axial guide slot and the said cylinder a lateral pro trusion engaging said guide slot for retaining the fuse charge in its safety position when said nose is retained in said casing.

14. A direct-action fuse according to claim 13, wherein the said locking means comprise a retaining sleeve slidably fitted between said casing and said cylindrical center portion thereof, the said sleeve being engageable with said protrusion of the cylinder for turning the fuse charge into its action position.

15. A direct-action fuse according to claim 14, wherein spring means within the casing cause movement of said retaining sleeve into engagement with the said protrusion upon release of said nose from the casing thereby effecting rotation of said cylinder into the action position of the fuse charge.

References Cited in the flle of this patent UNITED STATES PATENTS 2,076,602 Towner Apr. t3, 1937 FOREIGN PATENTS 85,362 Austria Sept. 10, 1921 761,133 France Jan. 3, 1934 

